Prevalence of recombinational versus mutational events in damaged plasmid DNA containing regions of homology with the chromosome

Mutat Res. 1991 Nov;264(3):127-34. doi: 10.1016/0165-7992(91)90129-r.


Plasmid DNA modified by in vitro treatments was transformed in E. coli bacterial cells. A streptomycin-resistant strain, carrying the peculiar rpsL421 mutation, was used as a recipient for the cloning vector pNO1523, which carries the wild-type (streptomycin-sensitive) rpsL allele. Transformants were streptomycin-sensitive unless a change in plasmid sequence had occurred. The analysis of the MaeI restriction pattern of plasmids isolated from streptomycin-resistant transformants, together with the detection of the phenotype that they conferred to a streptomycin-dependent strain, allowed us to identify plasmids that had undergone recombination with the host chromosome. The number of these plasmids exceeded by far that of plasmids resulting from mutational events.

MeSH terms

  • Chromosomes, Bacterial*
  • Cisplatin / pharmacology
  • DNA Damage
  • DNA, Bacterial / drug effects
  • DNA, Bacterial / genetics*
  • DNA, Bacterial / radiation effects
  • Deoxyribonucleases, Type II Site-Specific
  • Drug Resistance, Microbial / genetics
  • Escherichia coli / genetics
  • Ethyl Methanesulfonate / pharmacology
  • Mutagenesis*
  • Phenotype
  • Plasmids*
  • Polymorphism, Restriction Fragment Length
  • Recombination, Genetic*
  • SOS Response, Genetics
  • Sequence Homology, Nucleic Acid
  • Transformation, Bacterial
  • Ultraviolet Rays


  • DNA, Bacterial
  • Ethyl Methanesulfonate
  • CTAG-specific type II deoxyribonucleases
  • Deoxyribonucleases, Type II Site-Specific
  • Cisplatin